San Diego officials are proposing a variety of upgrades to Mission Bay Park’s Fiesta Island including new parks, playgrounds, volleyball courts, marsh areas and habitat preserves. The proposed master plan for the mostly undeveloped 470-acre island is envisioned as a balance between improving the island and retaining its rural ambiance, city officials said. While it would include some significant changes, city officials stress that the plan is less intense than some previous proposals for the island, which has occupied much of eastern Mission Bay since it was created by dredging in the 1940s.